Research On Performance Of Gas-liquid Two-phase Foam Nozzle

The paper was based on the fact that the higher expansion of aqueous film-forming foam(AFFF) used by civil airports, the better of the fire-fighting performance. In order to overcome the deficiencies of the vehicle mounted fire-fighting equipment, such as too low expansion, inhomogeneous foam and the instability of foam, this study carried out experiments on the performance of foam nozzle by using independent developed gas-liquid two-phase foam system. Two aspects were studied in this paper, (1) the effects of changed gas-liquid ratio on the foaming performance of AFFF were studied by precise controlling the rate of flow of gas and liquid; (2) the effects of the amount of foam net on expansion and draining time were studied by adjusting the number of foaming net.Through a series of experiments nearly 200 times, the results show that (1) the relationship between the expansion and gas-liquid ration is logarithm. When the gas-liquid ratio varies from 2.5 to 15, the gas-liquid ratio increases every 2.5 units, the ratio between foam volume and solution volume increases 3 units. When the gas-liquid ratio varies from 15 to 22.5, the gas-liquid ratio increases every 2.5 units, the expansion increases slow down, and keeps stability when reaches 18 units. Within the range of the effective amount of foam net, least square method were used to fit the relationship between foaming expansion and gas-liquid ratio, and the logarithm is E=A1+A2*ln(x); (2) when the gas-liquid ratio was increased,25% draining time was extended at first, and then shortened with the increasing of gas-liquid ratio, extended again when reached a ration, and finally keeps stable. When the gas-liquid ratio varies from 2.5 to 5, the 25% draining time was extended with the increasing of gas-liquid ratio. When the gas-liquid ratio varies from 5 to 10, the 25% draining time was shortened with the increasing of gas-liquid ratio. When the gas-liquid ratio varies from 10 to 22.5, the 25% draining time extended again when reached a ration, and finally keeps stable with the increasing of gas-liquid ratio; (3) the relationship between the expansion and the amount of foaming net is logarithm. Smaller fluid drops and higher foaming expansion can be acquired by increasing the amount of foam net. Gases make smaller fluid drops much easier to produce foam, reduce the capability of bringing liquid, pinch the thickness of concentrate foam liquid film, and extend waiting time of the process of draining liquid, that is extending 25% draining time.Above all, the performance of gas-liquid two-phase foam nozzle is better than the vehicle mounted fire-fighting system. The gas-liquid two-phase foam nozzle not only expands the range of foaming expansion, but also increases the stability of foam. So as to, the foam nozzle provides technical support for one minute firefighting requirements.